In a group of 11 older men, 2 mg of subcutaneous GHRH nightly for 6 weeks produced a relatively small increase circulating IGF-I but increases in muscle performance and urinary calcium excretion and no effects on body mass index, sleep profiles, or muscle bioenergetics. In a study of GH and sex steroid administration in old men and women, preliminary data show no significant baseline gender differences in GH release, IGF-I, OGTT glucose profiles, or plasma lipids. GH secretion was inversely related to ponderal index, fasting glucose and triglycerides, and positively correlated with levels of HDL. IGF-I was positively correlated only with triglycerides and IGF-BP-3 and not with GH release. Thus, in older men and women GH release may be a better predictor of metabolic and body composition than is IGF-I.